The present invention relates to a wiper blade for use in motor vehicles. In particular, it relates to means for effectively suppressing a possible reduction of wiper blade performance characteristics which may otherwise occur due to wind pressure etc., while a vehicle runs at a high-speed, and to a means for substantially improving aerodynamic characteristics of a wiper blade.
Many means have been used for the purpose of suppressing a possible reduction in the wiping performance of the wiper blade for motor vehicles, which may otherwise occur due to wind pressure at a high-speed. Various means may be listed for illustrative purposes including a device with plate-like blades. One blade may be adapted to provide a downward partial wind pressure force by forming a part of lever in a blade-like configuration, and one blade may comprise a wind deflector for shielding an air stream which strikes the blade rubber. In addition, an article may be provided in which a distance between the undersurface of the wind deflector and the glass surface is determined to be greater at the front of the air stream than at the rearward portion so as to generate a negative pressure between the undersurface of the wind deflector and the glass surface.
Such devices as those illustrated in FIG. 14 (DE.3139444), FIG. 15 (DE.3532536) and FIG. 16 (FR.262128) and the like can be cited as typical known arts, all of which may operate satisfactorily to some degree when vehicles run at a speed of around 150 km/h which is a conventional speed requirement for high-speed driving. However, it may be difficult for prior art devices to provide a satisfactory operation when the vehicles run at a speed of around 200 km/h which is a today""s common running velocity.
The device in FIG. 14 is designed to deflect an air stream which strikes the blade rubber 1 by means of wind deflector 2 which is provided at a position where it may shield the blade rubber 1. However, it might not shield the blade rubber 1 due to a reduced area of the wind deflector 2. In addition, an air stream which has passed through a space between levers may cause a disturbance, resulting in a lack of effective urging forces, to thereby create problems in that a substantial improvement during high-speed running might not be achieved.
The device shown in FIG. 15 is configured such that a lower edge 3 of the main yoke side wall extends in a spoiler design providing a particular inclined angle. However, it also causes a problem in that sufficient urging forces may not be produced since the air stream over the upper surface of the spoiler collides against the side wall of the main yoke, and thus the flow velocity is reduced, while simultaneously the air stream flowing over the undersurface of the spoiler is interfered with by a lever etc., to prevent a smooth flow of the air stream.
The device in FIG. 16 is designed to have a configuration in which a distance between the undersurface of the wind deflector 4 and the glass surface 5 is made greater at the front of the air stream than at the back side, thereby creating a negative pressure between the undersurface of the wind deflector 4 and the glass surface 5. This approach entails, however, a problem that it may not be effective unless the wind deflector 4 is provided at a lower position, and if the wind deflector is made to be wider to provide an effective result, the wind deflector 4 may interfere with the curved glass surface or the wind frame.
In the conventional devices as above-described, provision was made for means for improving wiper blade performance while a vehicle runs at high-speed. In particular, the devices were designed by taking aerodynamic characteristics into consideration which may occur either at the front side (upper surface in the drawing) or at a back side (lower surface in the drawing) of a wind deflector or a spoiler, based on a presumption that the air stream strikes the glass surface in a parallel manner. In contrast, the present invention is made with a presumption that an air stream is deflected upwardly as it interferes with the wiper blade, taking an air stream into consideration which acts against opposite surfaces of the wind deflector from the viewpoint of aerodynamic behavior. As a result, a most effective aerodynamic design has been realized.
In summary, in the wiper blade for use in motor vehicles a wind deflector is placed such that its side surface lying in front of the air stream may consist of an air stream-splitting section which may form a water-weir area at the rear-side of the air stream, a pressure-receiving surface section along the air stream which may create downward forces, and an air stream-weir section which may cause the air stream to flow at a reduced speed, as shown in FIG. 3. A height H between the lower edge of the air stream-splitting section in front of the air stream and the wind shield is greater than the height h of the blade rubber. In addition, there is a relationship between the height H and a clearance S to be formed between the upper end of the above-described air stream-weir section of the wind deflector and the main yoke, and this relationship is given as 1 greater than (S/H)xe2x89xa61/5 or preferably 1 greater than (S/H)xe2x89xa7(1/4). In addition, there may be a relationship between the length L1 of the pressure-receiving surface section and the length L2 of the air-stream weir section in the cross-section of the wind deflector, and this relationship is given as L1xe2x89xa7L2. Further, an angle xcex81 to be made between the pressure-receiving surface section and the glass surface is in a range of 0 less than xcex81xe2x89xa630xc2x0, and a relative angle xcex82 to be made between a plane of the air-stream weir section and a plane the pressure-receiving surface section is in a range of 30xc2x0xe2x89xa6xcex82xe2x89xa690xc2x0.
The air stream which flows along a wind screen is split into upper and lower flow components by means of an air stream-splitting section at the tip of the wind deflector. An upper air stream component flows along the pressure-receiving surface section, and rises upwardly while having its flow velocity reduced by means of the weir section. The lower flow component partially forms a virtual blade surface at a lower portion of the pressure-receiving surface section utilizing a water-weir area which is created backwards from the air stream-splitting section. Most of the lower flow component is caused to vary its flow direction upwardly while it flows along the virtual blade surface and the backward surface of the weir section to increase its flow velocity. The flow then passes through a space between the upper end of the weir section in the wind deflector and the side wall of the main yoke . Consequently, an in creased pressure is exerted on the upper surface e of the pressure-receiving surface section of the wind deflector, and a reduced surface pressure is provided to thereby generate downward forces (i.e. forces acting toward the wind screen).